The present invention relates to an endoscope system which has a bending portion formed from a hydropneumatic actuator on the distal end of an elongated insertion portion to be inserted into a tubular cavity and can be applied to, for example, an industrial endoscope and medical endoscope.
In general, an endoscope that can be applied to, for example, both an industrial endoscope and a medical endoscope has an elongated insertion portion to be inserted into a tubular cavity. An endoscope of this type has a bending portion on the distal end portion of the insertion portion. An operator can set the observation direction of the endoscope in an arbitrary direction by bending this bending portion.
As a bending portion attached to the distal end portion of an insertion portion, for example, a bending portion having a pneumatic actuator is described in Jpn. Pat. Appln. KOKAI Publication Nos. 4-135570 and 5-305053.
In addition, the bending portion described in Jpn. Pat. Appln. KOKAI Publication No. 5-76600 has a protective member around the outer surface of an actuator which changes in length in the axial direction and in diameter. This protective member restricts the expansion of the actuator in the radial direction.
A bending portion of this type includes an elastic tubular member on the distal end portion of an insertion portion. A plurality of pressurization chambers are arranged on the tube wall of this elastic tubular member along the circumferential direction. Pneumatic pressures are selectively supplied to the pressurization chambers to pressurize them. As a consequence, the elastic tubular member is bent in a direction opposite to the pressurized pressurization chambers.
An endoscope system is generally comprised of an endoscope body, a light source unit connected to the endoscope body, a CCU (Camera Control Unit), and the like. An endoscope system has been proposed, which has improved portability by housing the constituents of the system in one cart or a small case.
Consideration similar to that given to the endoscope system designed to improve portability in the above manner is given to an endoscope having a pneumatic actuator in a bending portion. The above conventional endoscope having the pneumatic actuator requires a relatively large compressor as a pneumatic source for bending the pneumatic actuator. For this reason, the endoscope system increases in size as a whole, and the portability deteriorates.
In the endoscope having the bending mechanism using the pneumatic actuator, the bending portion is bent by sending air supplied from the compressor, which is an external unit connected to the endoscope body, to the pneumatic actuator on the distal end side of the insertion portion through the air duct inserted into the insertion portion of the endoscope body.
If, however, the insertion portion of the endoscope is long, it takes much time to send air from the compressor to the pneumatic actuator. This causes a time lag in bending operation, and may interfere with accurate bending operation.
In addition, in the endoscope having the bending mechanism using the pneumatic actuator, the elastic tubular member of the bending portion is made of an extensible material such as silicone resin. A compressed fluid is selectively supplied to a plurality of pressurization chambers disposed on the tube wall of this elastic tubular member to pressurize the pressurization chambers, thereby bending the bending portion. A bend tube formed from an elastic tubular member, however, exhibits a unique phenomenon of hysteresis with respect to an increase/decrease in pressure. This makes it difficult to match bending operation using the operating portion at hand with the bending operation of the bending portion.
With a protective member like the one described in Jpn. Pat. Appln. KOKAI Publication No. 5-76600, which is placed around the outer surface of an elastic tubular member, an attempt has been made to restrict the expansion of the elastic tubular member in the radial direction by using the protective member as a restricting member when pneumatic pressures are supplied to pressurization chambers in the elastic tubular member so as to extend the pressurization chambers only in the axis direction, thereby efficiently bending the bending portion and preventing the bending portion from extremely expanding when it is bent.
A protective member like the one described in Jpn. Pat. Appln. KOKAI Publication No. 5-76600 is smaller in change amount than an elastic tubular member when extending in the axial direction. If, therefore, a protective member like the one described in Jpn. Pat. Appln. KOKAI Publication No. 5-76600 is placed around the outer surface of the elastic tubular member, the bending operation of the bending portion tends to be restricted by the protective member during the bending operation of the bending portion. This makes it difficult to set a large bending angle for the bending portion, posing a problem in improving bending performance.